Polyester resin coatings containing tetrakis(alkoxymethyl)benzoguanamines



United States Patent 32 Claims. (Cl. 260-22) This is a division ofapplication Serial No. 129,545, filed August 7, 1961, now U.S. PatentNo. 3,091,612.

This invention relates to novel alkylated methylol benzoguanamines; alsoit relates to organic solvent soluble baked finish surface coatingcompositions and storage stable water soluble baked finish surfacecoating compositions utilizing the novel alkylated methylolbenzoguanamines.

A novel group of alkylated methylol benzoguanamines has been discovered;these are the tetrakis(alkoxymethyl)benzoguanamines wherein each alkoxyhas 1-3 carbon atoms. Unexpected properties are possessed bybenzoguanamines of this class when at least two different carbon numberalkoxys are present in the molecule; to illustrate, one ethoxy and threemethoxys fortnin g mono ethoxymethyl tri (methoxymethyl benzoguanamine.An equilibrated mixture of compounds falling Within the defined class,wherein at least two diiferent carbon number alkoxys are present on anumber of the molecules such that the mixture is non-crystalline atordinary temperatures, is of particular utility in water soluble surfacecoating compositions.

It has been discovered that superior baked finish surface coatings areobtained from fluid compositions consisting essentially of a polyester,the defined benzoguanamine and an organic solvent for the polyester andthe benzoguanamine. These polyesters are obtained from certain benzenetricarboxylic acids, a'lkylene glycols and alkanedioic acids.

It has also been discovered that exceptional storage stability ispossessed by Water soluble compositions consisting essentially of awater soluble form of the abovementioned polyester, the above-mentionedbenzoguanamines wherein at least two different carbon number alkoxys arepresent in the molecule-or an equilibrated mixture thereon-and water.

THE ALKYLATED METHYL BENZOGUA- NAMINES The novel alkylated methylolbenzoguanamines of the invention are thetet-rakis(alkoxymethyl)benzoguanamines wherein each alkoxy constituenthas 1-3 carbon atoms. These compounds may also be named N,N,N, Ntetrakis(alkoxymethyl) 2,6 di-amino 4 phenyls-triazi-ne where eachalkoxy constituent has l3 carbon atoms. In other words, the alkoxyconstituent (R-O-) contains an .a-lkyl group which may be methyl, ethyl,r1- propyl, or isopropyl. Illustrations of these benzoguanamines whereinall the alk-oxys have the same number of carbon atoms are:N,N,N,'N'-tetrakis(methoxymethyl) 2,6 diamino 4 phenyl s triazine;N,iN,N,'N'- tetrakis(ethoxymethyl) 2,6 diamino 4 phenyl striazine, andN,N,N,N' tetrakis(isopropyloxymethyl)- 2,6-diamino-4-phenyl-s-triazine.

Those compounds are included in the scope of the invention wherein .atleast one alkoxy constituent has a dilferent number of carbon atoms thanthe other alkoxy constituents. These may be defined as tetrakis(alkoxy-"ice methyl)benzoguanamines wherein each alkoxy has from 1-3 carbonatoms and at least one alkoxy has a different number of carbon atomsthan the others. Illustrations of these chemically-mixed benzoguanaminesare: di(ethoxymethyl)di(methoxymethyl)benzoguanamine,mono(ethoxymethyl)tri(methoxymethyDbenz gu anamine, diisopropyloxymethyl) di (methoxymethyl) benzoguanamine andtri(ethoxymethyl)mono(isopropyloxymethyl)benzoguanamine.

It has been observed that the defined benzoguanamine wherein all of thealkoxy constituents have the same number of carbon atoms are crystallinesolids at ordinary temperatures. Herein ordinary temperatures areintended to include the range of about 50 F.-l00 F. Unexpectedly, thedefined benzoguanamines where in at least one alkoxy has a differentnumber of carbon atoms than the other alkoxys are characterized by thenon-crystalline state at ordinary temperatures. The term non-crystallineis intended to include liquids which are fairly mobile, viscous liquidsand glass-like materials.

It has been observed that a physical mixture of twotetrakis(alkoxymethyl)benzoguanamines differing only in the number ofcarbon atoms in the alkoxy constituents, for example,tetrakis/(methoxymethyl)benzoguanamine andtetralcis(ethoxymethyl)benzoguanamine, do not blend to a material whichis non-crystalline at ordinary temperatures. However, it is possible toobtain a mixture which includes benzoguanamines containing only one typeof alkoxy, which mixture is characterized by the non-crystalline stateat ordinary temperatures, This mixture is the equilibrated mixtureobtained when tetramethylol 'benzoguanamine is simultaneously alkylatedwith materials affording at least two different carbon number reactants.To illustrate: the equilibrated mixture produced when tetramet-hylolbenzoguanamine is alkylated with a mixture of ethanol and methanol or amixture of methanol and isopropanol includes benzoguanamines havingchemically mixed alkoxy constituents and also molecules having only onetype of alkoxy constituent. For convenience, the proportion of alkoxyconstituents of one carbon number and alkoxy constituent of anothercarbon number present in an equilibrated mixture are based on thealkylating compound charged to the alkylation reaction. Only a smallamount of the different alkoxy affording compound is needed to obtainthe equilibrated product characterized by the non-crystalline state. Theexact amount of dilferent alkoxy affording compound is dependent uponthe type of alkoxy constituents desired to be present in the finaltetr-akis(alkoxymethyl)benzo- 'guanamine mixture. In general, 10% on amolar basis of the alkoxy constituents present in the mixture differingin carbon number from the other alkoxy constituents will produce anequilibrated mixture of the desired noncrystalline state. Specificillustrations of equilibrated mixtures are: the equilibrated mixtureobtained when the alkoxy constituents are derived from ethanol andmethanol; in one instance, the molar ratio of the 1 carbon alkoxy to 2carbon alkoxys is about 1the ethanol/methanol molar ratio charged to thealkylation reaction being about 1; in another instance, the molar ratioof 1 carbon alkoxy to 2 carbon alkoxys is about 3-the molar ratio ofmethanol/ethanol charged to the alkylation reaction is about 3.

The defined benzoguanamines are of low solubility in water; even theequilibrated mixtures are low in water solubility. All of the definedbenzoguanamines possess substantial solubility in organic solventscommonly used in the surface coating industry.

Hereinafter, there is set forth a preparation of tetramethylolbenzoguanamine and 4 illustrative benzoguanamines coming within thescope of the invention.

3 EXAMPLES Terramethylol benzoguanamina-Five hundred forty grams of 37%formalin was brought to pH 8 with NaOH and heated to 75 C. Two hundredgrams of benzoguanamine was stirred into the solution. Reaction occurredrapidly giving complete solution in five minutes. The solution was thencooled to precipitate tetramethylol benzoguanamine. It was filtered offand dried overnight in a circulating air oven at 40 C. It melted at ca.132 to 142 C.

' Example 1 Tetrakis(methoxymethyl) benzguanamine.TWo hundred grams oftetramethylol benzoguanamine was slurried in 600 ml. of methanol at roomtemperature. Then with rapid stirring 28.2 ml. of concentratedhydrochloric acid was added. The nature of the solid material insuspension changed from an amorphous white solid to colorlesscrystalline material. Stirring was continued 15 minutes and then sodiumbicarbonate was added until CO was no longer evolved. The solid productwas filtered off and recrystallized from hot water to produceneedle-like crystals of M.P. 92 C. This analyzed for 56.14% C, 7.31% H,and 19.29% N. Theoretical for tetrakis (methoxymethyl)benzognanamine:56.2% C, 6.94% H, and 19.3% N.

Example 2 T etrakis(eth0xymethyl benzogzmnamine. Two hundred grams oftetramethylol benzoguanamine was slurried with 600 ml. of absoluteethanol at room temperature. Then with rapid stirring 28.2 ml. ofconcentrated hydrochloric acid was added. After 15 minutes of stirringcomplete solution had taken place. Sodium hydroxide was then added untilthe pH was 8. The mixture was filtered from NaCl then concentrated invacuum to 5 mm. pressure and 90 C. The crude benzoguanamine etherweighed 194 g. On cooling, it slowly solidified to lowmelting waxycrystals. It was difficult to recrystallize. Some of it was dissolved ina mixture of formamide and ethanol and left to evaporate. This techniqueslowly gave crystals of pure tetrakis(ethoxymethyl)benzoguanamine ofM.P. 60 C. sharp. Analysis for nitrogen showed 17.1%; theoretical is16.7%.

Example 3 A mixture of 200 g. tetramethylol benzoguanamine, 50.1 g. ofmethanol, and 72.0 g. of ethanol was stirred to a paste, then 28 ml. ofconcentrated hydrochloric acid was added. A mildly exothermic reactiontook place yielding near solution in 2 minutes. Five minutes later asolution containing 50.1 g. of methanol and 72.0 g. of ethanol wasadded. The overall molar ratio of the two alcohols was 1. Stirring wascontinued an additional 7 minutes to give complete solution. Sufiicient20% NaOH Was then added to bring the pH to 8. The two phase liquid wasthen evaporated on a steam bath under reduced pressure until only aliquid organic phase and a solid (sodium chloride) phase was present.The solid was removed by filtration under pressure to yield anequilibrated mixture of methyl ethyl ethers of tetramethylolbenzoguanamine. The material remained liquid after several weeksstorage. One-half gram of this product could not be dissolved in 100 g.of water.

Example 4 Two hundred grams (0.65 mole) of tetramethylol benzoguanaminewas agitated with 150 g. (4.7 mole) of methanol and 72 g. (1.57 mole) ofethanol at 25 C. The overall molar ratio of methanol/ ethanol was 3.Twentytwo milliliters of concentrated (96%) sulfuric acid was then addedover a half-minute period. The mixture exothermed to ca. 50 C. andcomplete solution was obtained in 2 minutes. Ten minutes after acidaddition, the solution was neutralized to pH 8 by the careful additionof about 120 ml. of 20% NaOH. This addition required ILLUSTRATIVESURFACE COATING COMPOSITIONS A phthalic anhydride type polyester resinwas prepared by introducing 3 moles of phthalic anhydride, 3 moles oftrimethylol propane, 1 mole of neopentyl glycol and 1 mole of adipicacid into a glass vessel. This vessel was provided with a propellerstirrer, a thermometer, a sparge tube of introducing nitrogen, and acondenser for removing water produced in the polycondensation reaction.The temperature in the vessel was gradually increased until 400 F. wasreached. The materials in the vessel were held at this temperature untilthe product had an acid number (mg. KOH/ g.) of 50.

The polyester was dissolved in a 60-40 xylene-butanol solvent. Titaniumdioxide was added to the solution in a ratio of 0.9 part by Weight oftitanium dioxide to 0.8 part by weight of polyester. In one instance,tetrakis (methoxymethyl)benzoguanamine was blended into the pigmentedpolyester solution to a level of 30 parts by weight of thebenzoguanamine for parts by weight of the polyester resin. In anotherinstance, tetrakis(ethoxymethyl)benzoguanamine was blended into thepigmented polyester solution to a level of 20 parts by weight of thebenzoguanamine for parts by Weight of the polyester resin. Panels wereprepared by applying the pigmented blends to bonderized steel plates.The coated panels were baked in an oven for 30 minutes at 300 F. Thebaked finish on each panel was measured and found to be 1.3-1.5 mils inthickness.

The cured panels were tested in accordance with standard testingprocedure; these tests Were impact in inch pounds; flexibility when bentabout a /s inch mandrel; resistance to staining by iodine; resistance tosoftening by acetone; resistance to 2 percent (NaOH) solution for 16hours; and resistance to marring.

The phthalic anhydride polyester-tetrakis(methoxymethyl)benzoguanamine70:30 blend panels at an impact resistance of 2 inch pounds; cracks wereevident in the flexibility test; the films passed the iodine, theacetone and the 2 percent (NaOH) test; the film failed the marresistance test.

The phthalic polyester-tetrakis(ethoxymethyl)benzoguanamine 80:20 blendpanels at an impact test of 2 inch pounds; cracks were present at thebend in the flexibility test; the films passed the acetone, the 2percent (NaOH) and the mar resistance tests; the films failed the iodinestain test.

It is considered that the phthalic polyester-defined benzoguanaminesurface coating compositions are acceptable by present commercialstandards for baked finishes which do not require high impact strengthand exceptional flexibility.

ORGANIC SOLVENT SOLUBLE BAKED FINISH SURFACE COATING COMPOSITIONS Thepolyester resin The acidic member reactant in the preparation of thepolyester resin (polycondensation reaction product) is an unsubstitutedbenzene tricarboxylic acid or of the corresponding anhydride; these aretrimellitic acid, trimellitic anhydride, hemimellitic acid, hemimelliticanhydride, and trimesic acid.

The polyester resin portion of the composition consists essentially ofthe polycondensation reaction product of one of the above defined acidicmembers with an alkylene glycol having 2-10 carbon atoms and analkanedioic acid having 4-1() carbon atoms. The acidic member, the

glycol, and the alkanedioic acid may be charged to the polycondensationreaction in a number of molar ratios. The molar ratio of acidicmember/glycol/alkanedioic acid charged falls in the range of 2.3/7/3 to32/7/05; the carboxyl group (COOH) afifording reactants charged and thehydroxyl group (OH) affording reactants charged are controlled toprovide a molar ratio of hydroxyl groups/carboxyl groups within therange of 1.05 to 1.40. In other words, there is present in the reactionzone an excess of hydroxyl groups of roughly about 40%. Thepolycondensation reaction is continued until a product is obtained whichis characterized by an acid number of about 25-80. Acid number hereinmeans the milligrams of KOH used per gram of polyester.

The alkylene glycols may be either simple glycols or ether glycols whichhave from 2 to carbon atoms. Illustrations of these alkylene glycols areethylene glycol, proplene glycol, 1,4-butanediol, neopentyl glycol, 1,3-hexanediol, diethylene glycol, dipropylene glycol triethylene glycol,tetraethylene glycol and decanediol. Usually, the glycols having 410carbon atoms are used. Especially good results are obtained with thebutanediols and pentanediols.

The polyester requires the presence of alkanedioic acid having 4l0carbon atoms. It is preferred to use the acids containing 6-7 carbonatoms. Illustrative alkanedioic acids are succinic, glutaric, adipic,pimelic, suberic, azelaic, and sebacic. It is to be understood that theanhydrides of these acids may also be utilized.

For some purposes, it is desirable to modify the straight acidicmember-glycol-alkanedioic acid polyester resin by introducing into thereaction a modifier which may be either an alkane monocarboxylic acidhaving 6l3 carbon atoms or an alkane monohydric alcohol having 4-13carbon atoms. The alkane monocarboxylic acids are saturated aliphaticacids containing only carbon, hydrogen, and oxygen atoms. Illustrativeof these alkane monocarboxylic acids are caproic, enarthic, caprylic,pelargonic, capric,n-undecyclic, lauric and tridecanoic.

The alkane monohydric alcohols are saturated monohydric aliphaticalcohols having only carbon, hydrogen and oxygen atoms. Illustrative ofthese alkane monohydric alcohols are butyl, amyl, caproyl, capryl,undecyl, and lauryl. Particularly suitable of these alcohol modifiersare mixtures obtained by the Oxo process; commercially available Oxoalcohols are isooctyl alcohol, noyl alcohol, decycl alcohol, andtridecyl alcohol.

The reactants in the preparation of the polyester are charged in molaramounts such that an excess of hydroxyl groups is present in thepolycondensation reaction zone. The molar ratio hydroxyl groups/carboxylgroups provided by the hydroxyl group affording reactants and thecarboxyl group affording reactants is controlled within the range of1.05/l to 1.40/1. The amount of excess hydroxyl groups will bedetermined in each instance by the requirements of the particularpolyester.

For convenience in setting forth the proportional molar amounts of thethree essential reactants, the glycol reactant has been held at seven(7). The desired resin is obtainable while varying the proportionalmolar amount of the defined acidic member over the range of about 2.3 to3.2. The alkanedioic acid molar proportion is varied over the range of0.5 to 3. In order to obtain the desired polyester resin, theproportional molar amounts within the reaction system of acidic member/glycol/alkanedioic acid is held in the range of 2.3/7/3 to 32/7/05. Whenone or more modifiers are present, commonly the alkanedioic acid amountand acidic member amount are adjusted, within the above ranges, toprovide proportional amounts of reactants giving an excess of hydroxylgroups falling within the hereinabove defined range.

The acidic member, the defined glycol, and the alka nedioic acid arecondensed under the well-known polycondensation reaction conditions. Ingeneral, the polycondensation reaction is carried out at a temperaturebetween about 200 F. and about 450 F., and more usually about 300 F. Thereaction is carried out under an inert atmosphere, with continuousremoval of water of reaction and for a time producing the desired acidnumber. When operating with the anhydrides at the lower acid numberproducts, it is desirable to observe the reacting mixture closely whenapproaching the completion of the reaction; the reaction mixture has atendency to reach the gel point in a more or less abrupt fashion.However, observation of the reaction zone permits ready completion ofthe reaction without gelation.

The polycondensation reaction is continued until the product has an acidnumber between about 2580; more usually this acid number is about 3050.Polyester resins having this acid number produce superior bakedfinishes, and are readily converted to the water soluble forms.

The defined benzoguanamines In the organic solvent soluble composition,a tetrakis- (alkoxymethyl)benzoguanamine, or mixtures thereof, ispresent in a hereinafter defined proportion; these benzoguanamines maybe any one of those hereinabove defined.

The organic solvent The polyester resin and the defined benzoguanamineare physically blended in hereinafter set out proportions. The twofilm-formers are dissolved in an organic solvent. Sufficient organicsolvent is present to form a fluid composition. It is to be understoodthat the degree of fluidity is determined by the particular applicationof the composition, i.e., brush, gun or roller, and also by thetemperature at which the composition is applied to the surface. In thecase where pigments, etc., are present, fluidity will also be determinedby the particular mode of application.

Any of the organic solvents commonly used in the surface coatingindustry for alkyd resins and polyester resins may be utilized forobtaining the desired fluidity. In some instances, it may be desirableto use solvents which are not evaporated from the film during the curingoperation. However, ordinarily the solvents will be materials whichvolatilize before or during the curing operation. Illustrations ofcommonly used organic solvents are set out hereinafter. Ketones:acetone, methyl ethyl ketone, diethyl ketone, cyclohexanone, diacetonealcohol, acetophenone, diisobutyl ketone. Ethers and polyethers:1,4-dioxane, 1,2-diethoxyethane (diethyl Cellosolve), diisopropyl ether,diethylene glycol diethyl ether (diethyl Carbitol). Esters: ethylacetate, isopropyl acetate, isobutyl acetate, Z-methoxyethyl acetate(methyl Cellosolve acetate), 2-ethoxyethyl acetate (Cellosolve acetate),2- (2 ethoxyethoxy)ethyl acetate (Carbitol acetate). Ether-alcohols:Z-ethoxyethanol (Cellosolve), 2-(2-ethoxyethoxy)ethanol (Carbitol),di-propylene glycol monoethyl ether. Alcohols: methanol, ethanol,l-butanol, isobutyl alcohol, cyclohexanol, n-octyl alcohol, 2-ethylhexylalcohol.

In some instances, aromatic hydrocarbon solvents may be used alone; morecommonly, these are admixed with one or more of the above listedsolvents and particularly with the alcohols. Illustrative aromatichydrocarbons are: benzene, toluene, xylene, ethylbenzene, tetralin.

Parafiinic hydrocarbon solvents may :also be used in some instances.Illustrative of these solvents are: paint and varnish makers naphtha andstandard mineral spirits.

Proportions The hereinabove defined polyester and the hereinabovedefined benzoguanamine are present in the final composition inproportions by weight to make 100 parts of polyesterzbenzoguanamineblend. The blend ranges in proportion from parts of polyester:5 parts ofbenzoguanamine to 30 parts of polyester:70 parts of benzoguanamine.Superior baked finishes are obtained when the acid, 1.75. is 3/ 8/2.Using the equipment and procedure set forth proportion ofpolyester:benzoguanamine in the blend ranges from about 80 parts ofpolyester:20 parts of benzoguanamine to 70 parts of polyesterz30 partsof benzoguanamine.

The composition Both the defined polyester and the definedbenzoguanamine are soluble in the hereinabove defined organic solvents.The polyester and the defined benzoguanamine may be added to theparticular solvent at ordinary temperatures in the desired proportionsto obtain the fluid composition. It may be convenient to prepare asolution of the polyester in the desired organic solvent and then addthe particular defined benzoguanamine to that solution to obtain thefinal fluid composition.

The fluid compositions are storage stable and do not changecharacteristics during storage.

The fluid compositon consisting only of the polyester, the definedbenzoguanamine and organic solvent therefor may be used for clear bakedfinishes which may range from water-white clarity to opaque browncoloring. Enamel finishes may be obtained by adding pigments, extendersand dyes, if desired, to the clear composition. These baked enamelfinishes are distinguished by a brilliant gloss and toughness.

The wet films positioned on the surface to be coated are cured by bakingat elevated temperatures for the necessary time. In general, 30 minutestime at 300 P. will give complete cures of substantially all thecompositions. It is to be understood that temperatures higher than 300F. may be used when shorter curing times are desired. The particularcuring time will be dependent somewhat on the type and amount of thedefined benzoguanamine present in the compositions.

EXAMPLES Tests were carried out on baked films obtained from severalcompositions illustrative of the invention. Also, tests were carried outon panels prepared from phthalic polyesters admixed with two of thedefined benzoguanamines. Also, panels were tested which had beenprepared from a mixture of the defined polyester resin and tetramethylolbenzoguanamine.

The polyester resin portion of the compositions of The above trimelliticpolyester was dissolved in a -40 xylene-butanol solvent. Rutile titaniumdioxide was added to the solution in a weight ratio of 0.9 part ofdioxide to 0.8 part of polyester. This pigmented solution was used as abase to prepare a number of benzoguanamine containing enamels. Three ofthese enamels were prepared using tetramethylol benzoguanamine (Nos.1-3, Table I). Two enamels containedtetrakis(methoxymethyl)benzoguanamine (Nos. 4-5, Table I). Three enamelscontained tetrakis(ethoxymethyl)benzoguanamine (Nos. 6-8, Table 1).

Using the pigmented solution of phthalic polyester previously describedin column 4, six enamels were prepared. Three enamels containedtetrakis(rnethoxymethyl)benzoguanamine (Nos. 9-11, Table I), and threeenamels contained tetrakis(ethoxymethyl)benzoguanamine (Nos. 12-14,Table I).

Cured, coated panels were prepared by applying the various enamels toBonderized steel plates; the curing was carried out in a heated oven at300 F. for 30 minutes.

The baked film on each panel was measured and was tested in acc-ordancewith the various standard testing procedures, i.e., impact, flexibilitywhen bent about an /s mandrel, resistance to staining by iodine,resistance to softening by acetone, resistance to 2% (NaOH) solution for16 hours, and resistance to marring.

The enamels used in the tests and the properties of the baked film areset out in Table I. The results show that tetramethylol benzoguanaminein the defined polyester (Nos. 1-3) is definitely poor with respect tothe other enamels; except that the impact strength is better than thatof the phthalic polyester containing enamels (Nos. 9-14). The enamels ofNos. 48-illustrative of the compositions of the inventionare vastlysuperior to the phthalic polyester enamels (Nos. 9-14), and the enamelsof Nos. 1-3. These enamels of the invention are also superior inflexibility and, in general, better in the resistance properties thanthe phthalic polyester enamels and the tetramethylol benzoguanamineenamels. Considering the chemical difference between the phthalicanhydride and the trimellitic anhydride polyesters, the vast superiorityof the enamels containing the trimellitic anhydride polyester is mostunexpected.

TABLE I.BAKED FILM PROPERTIES FROM SOLVENT COMPOSITIONS 1 "Benzo- FilmResistance to Polyester, guana- Thick- Impact, Flex1- Number Wt. mlneWt. ness, Inch bility 4 percent 1 percent 3 Mils Lbs. 2%

Iodine Mar Acetone NaOH 16 hrs.

90 10 0.9 18 P F F F F 80 20 1. 1 16 P F F F F 30 1.. 0 10 P F F P P 9010 1.0 P F F P P 80 20 1.1 80+ P P F P P 10 0.9 80+ P P F F F 80 20 1.080+ P P F P P 70 30 1.1 80+ P F F P P 90 10 1. 4 2- F F F F F 80 20 l. 32- F F P P P 70 30 1. 3 2- F P F P P 90 10 1. 5 2- F P F F F 80 20 1. 52- F F P P P 70 30 1. 3 2- F P P P P 1 Solvent: Xylene, 60%; Butanol,40%.

2 Polyester: Nos. 1-8, see trimellitic polyester, column 7. Nos. 9-14,seephthalic polyester, column 4.

3 Nos. l-3: tetramethylol benzoguanamine. Nos. 4-5 and 9-11:tetrakis(methoxymethyl)benzoguanamine. Nos. 6-8 and 12-14: tetralris(ethoxymethyl)benzoguanamine.

4 inch mandrel. 5 P=Pass; F=Fail. Remarks:

the invention was prepared using molar proportions of trimelliticanhydride, 2.6; neopentyl glycol, 7; and adipic In round numbers, thismolar proportion in the preparation of the phthalic polyester in column4, a trimellitic polyester resin was prepared having an acid number of50.

WATER SOLUBLE BAKED FINISH COATING COMPOSITION Formation of the watersoluble polyester The water soluble material contains polyester resin(polycondensation product), as hereinabove described, reacted with analkaline reacting agent to obtain a water soluble material. Thepolyester resin and the agent are reacted until a water soluble form isobtained. Usually enough agent is used to neutralize the acidity of thepolyester resin; less may be used. The amount of alkaline reactingmaterial is most readily determined by following the pH of the aqueousmedium. The polyester resin passes into solution substantiallycompletely at pH of about 5. In practically all instances, the polyesterwill be in a complete solution at a pH of about 6. The use of alkalineagent in excess of that needed to bring all the polyester into solutionis not harmful, at least up to a water solution pH of about 8. It ispreferred to have the aqueous solution somewhat on the acid side orneutral, i.e., a pH of from 6 to 7.

The alkaline reacting agent may be ammonia or alkyl amine, orheterocyclicamine or an alkanolamine. Ammonium hydroxide as the aqueoussolution containing 28% is suitable. The alkyl amines, particularly thelower molecular weight amines containing not more than 4 carbon atoms ineach alkyl group, are especially suitable. The alkanolamines, such as2-amino-2-methyl-lpropanol, ethanolamine and dimethylethanolamine, arepreferred. The heterocyclicamines, such as morpholine, pyridine, andpiperidine may be used. The type of alkaline reacting material used isdetermined in part by the characteristics desired in the final watersoluble polyester; also, by the type of polyester which is to beconverted to a water soluble form.

The solubilization reaction is carried out by contacting the polyesterresin and the aqueous alkaline reacting medium. It is preferred that itbe warm, i.e., maintained in the region of l00l60 F. The two areagitated until the polyester resin has passed into solution. The watersolutions of the water soluble polyester resin are clear liquids usuallycontaining some opalescent appearance; the solutions may be colorless orcolored, depending on the particular water soluble polyester present.

The n0n-crystu-lline lelrakis(alk0xymelhyl) benzoguanamines Previouslythere had been defined a group of tetrakis (alkoxymethyl)benzoguanamineswhich are at ordinary temperatures non-crystalline, i.e. liquids; eithermobile liquids, viscous liquids or glass-like materials. In thesenon-crystalline chemically-mixed benzoguanamines, each alkoxy has 1-3carbon atoms and at least one alkoxy is a different carbon number thanthe others. The chem ically-mixed benzoguanamines include equilibratedmixtures wherein each alkoxy has 1-3 carbon atoms, and at least twodifferent carbon number alkoxys are present on a number of thebenzoguanamine molecules such that the mixture is non-crystalline atordinary temperatures. It has been pointed out that, in general, aslittle as 10% of the alkoxys present in the mixture differing in carbonnumber from the other alkoxys will produce a non-crystallineequilibrated mixture.

It has been observed that all of the hereinabove definedtetrakis(alkoxymethyl)benzoguanamines can be brought into solution in awater solution of the hereinbefore defined polyester resin to obtain awater soluble composition which produces good baked finish surfacecoatings; however, when all of the alkoxy constituents in the particulartetrakis(alkoxymethyl)benzoguanamine have the same carbon number, thewater soluble composition has no significant storage stability. Forexample, tetrakis(methoxymethyl)benzoguanamine and tetrakis-(ethoxymethyl)benzoguanamine precipitated out of solution in periods upto about one day after the solution was formed. When thechemically-mixed tetrakis(alkoxymethyl)benzoguanamines are used to formthe solution, a true compatible solution is formed which apparently hasindefinite storage life.

The water soluble composition of the invention is obtained by dissolvingthe non-crystalline tetrakis(alkoxymethyl)benzoguanamine in an aqueoussolution of the polyester resin. It need be, the non-crystallinebenzoguanamine is melted and then added to a preformed aqueous solutionof the polyester resin. However, the polyester resin may be intermingledwith the non-crystalline benzoguanamine and the mixture introduced intowarm water containing the solubilizing alkaline material. Thus,simultaneously the aqueous solution of polyester resin and the finalwater soluble composition, in water solution, is obtained. In anothervariant of the operation, the non-crystalline benzoguanamine may bedissolved in a solution such as ethanol and this solution added to theaqueous solution of the polyester resin. Or in still another variation,a solution of resin and non-crystalline benzoguanamine may be formed inethanol or acetone and this solution then treated with aqueous alkalinematerial to obtain the water soluble composition in aqueous solution.

The defined mixed benzoguanamines are only slightly soluble in water,however, when added to a water solution of the defined polyester resin,the mixed benzoguanamine readily passes into solution to form acompatible system of good storage life. Surprisingly, a very largeamount of the mixed benzoguanamines can be taken into the water solutionof the polyester resin and permit compositions containingpolyesterzmixed benzoguanamine blends ranging from 95:5 to 30:70, moreusually, 85:15 to 40:60.

Preferably the compositions contain a proportion of polyesterzmixedbenzoguanamine blend in proportions ranging from about :20 to 70:30.

The water solution may be used as such to form baked varnish-like filmswhich range from water white to brown coloring. Water soluble enamelcompositions may be obtained by adding pigments, extenders, and dyes, ifdesired, to the clear water soluble composition. Surprisingly, the bakedenamel finishes obtained. from water solution posses the brilliant glossas well as the toughness of the enamel finishes obtained from organicsolvent compositions.

The water soluble compositions have curing rates essentially the same asthe organic solvent compositions. In general, 30 minutes at 300 P. willgive complete cures of substantially all the compositions. Temperatureshigher than 300 F. may be used when shorter curing times are desired.The particular curing time will be dependent somewhat on the type andamount of the defined mixed benzoguanamine present in the composition.

EXAMPLES A water solution of trimellitic polyester resin preparedaccording to the procedure set out in column 7 was dissolved in warmwater containing dimethyl ethanolamine. The water solution containedapproximately 40 weight percent of the resin solid. Rutile titaniumdioxide was dispersed in the resin solution in a weight ratio of 0.9part of dioxide to 0.8 part of polyester resin. This pigmented solutionwas then used as a base in the preparation of hereinafter describedenamel formulations.

No. 15: Tetramethylol benzoguanamine was agitated with the pigmentedsolution. The tetramethylol benzoguanamine did not pass in solution atordinary temperature nor did mild heating of the mixture cause thetetramethylol benzoguanamine to pass into solution.

No. 16: With the aid of mild heating, tetrakis(methoxymethyl)benzoguanamine readily passed into solution in thepigmented solution. Two formulations were prepared; one contained 20parts of the benzoguanamine and 80 parts of the water soluble polyesterresin, the other contained 30 parts of the benzoguanamine and 70 partsof the water soluble polyester. When freshly prepared,

results of testing the cured panel are set out in Table II. No. 22 showsthat this formulation is equally as good as similar formulations usingthe equal molar ratio of ethoxy and methoxy constituents of Example 3.

TABLE II.BAKED FILM PROPERTIES FROM WATER COMPOSITIONS Resistance to-Polyester, Benzo- Film Impact, No. Wt. guanamiue, 'Ihick- Inch Flexi-Percent 1 Wt. ness, Lbs. bility 3 4 2% Percent 2 Mils Iodine Mar AcetoneNaOH,

16 hrs.

92.5 7.5 0.8 80+ P F F F F 90 0.8 80+ P F F I F 85 0.8 80+ P P P P P 7030 0.8 80+ P P P P P 55 45 0.8 80+ P P P P P 80 1.0 80+ P P P P P 1 Nos.17-22z see trimcllitic polyester, column 7. I 2 Nos. 17-21:equilibriated mixture of Example 3, column 3. N 0. 22; equrllbriatedmixture of Example 4,

columns 3 and 4.

3 1 8 inch mandrel. 4 P=Pass; F=Fail.

produced enamel formulations, and baked for minutes at 300 F. The curedfilms had impact strengths of 80+ inch pounds and passed all the otherstandard tests. These tests show that in spite of the lack of storagestability, freshly prepared formulations of the water soluble enamel canproduce superior baked films.

Formulations with mixed benzoguanamines Another portion of thepreviously described trimellitic polyester resin was dissolved in waterusing dimethyl ethanolamine as the alkaline agent; this solutioncontained 38 percent by weight of the polyester resin. Some of theequilibrated mixture of methoxy and ethoxy containing benzoguanarninesof Example 3, described in column was added to the polyester solution.The mixed benzoguanamine rapidly passed into solution to produce a clearhomogeneous formulation containing 70 parts by weight of .the watersoluble polyester and 30 parts by weight of the mixed benzoguanamine.This formulation, after several days standing, was still clear-in onephaseand showed no evidence of benzoguanamine coming out of solution. Apanel was prepared from the clear solution and baked for 30 minutes at300 F.; the cured film was clear and very tough.

Nos. 17-21: Using the 38 percent polyester resin solids aqueous solutiondescribed above as a base, a pigmented solution was prepared bydispersing rutile titanium dioxide therein at a ratio of dioxide toresin of 0.9/0.8. Several test formulations were then prepared bydissolving into the pigmented solution various amounts of theequilibrated methoxy and ethoxy containing benzoguanamine of Example 3,described in column 3. Panels were prepared from these enamelformulations and cured at 300 F. for 30 minutes. The result of thetesting of the baked films is set out hereinafter at Table II. All ofthese baked films were distinguished by extremely high gloss; this glosswas fully the equal of the gloss obtained from formulations usingxylene-butanol solvent. The high impact strength and good flexibilityshown by all of the enamel formulations of Nos. 17-21 permit even thepoor performing low mixed benzoguanamine content formula tions to havecommercial acceptance for some uses.

No. 22: An enamel formulation was prepared by adding the equilibratedmixture of methoxy and ethoxy containing benzoguanamines of Example 4described in columns 3 and 4. This benzoguanamine rapidly passed intosolution in the pigmented solution described above. This particularenamel formulation contained 20 parts by weight of the mixedbenzoguanamine of Example 4 and 80 parts by weight of the trimelliticpolyester resin in Water soluble form. A panel was prepared from thisformulation and cured at 300 F. for 30 minutes. The

Portions of the formulations Nos. l7-22 have been standing in storagefor several weeks and it appears that the formulations will have anindefinite storage stability, since in all previous experiments, lack ofcompatibility has been self-evident in a period of approximately oneday.

As a matter of information, panels prepared from the water soluble formof the above described trimellitic polyester resin, in the absence ofthe defined benzoguanamines, do not form cured films when baked at 300F. for 30 minutes. These films did not cure completely until exposed forat least 30 minutes to a least 400 F. temperature.

COMPARISON l-2 RESIN COMPOSITIONS In a previous study with another classof alkylated melamines, it was observed that polyester resins preparedfrom trimellitic anhydride and alkylene glycol only could be dissolvedin water along with the melamine and baked at 300 F. for 30 minutes togive very good films. For purposes of comparison, formulationscontaining such a polyester resin (hereinafter called 1-2 resin) andequilibrated mixed benzoguanamines of Example 3 described in column 3were prepared. These formulations were prepared as follows:

The 1-2 resin was prepared by cooking a charge of 5.53 moles ofneopentyl glycol and 2.50 moles of trimellitic anhydride for 4 /2 hoursat 350 F. until the acid number was 52.

This resin was dissolved in water by the usual procedure usingdimethylethanol amine. The solution was then pigmented with rutile TiOin the ball mill to a TiO l resin weight ratio of 1.12. The equilibratedbenzoguanamine of Example 3, in column 3, was then mixed with thepigmented solution to form a water soluble enamel composition; fiveenamels were prepared. Wet films were then baked at 300 F. for 30minutes on Bonderite steel panels.

The resin-mixed benzoguanamine blends were 90: 10; :20; 70:30; 50:50;and 30:70, respectively. The baked films were 0.8-0.9 mil thickness. Theimpact strength ranged from 2 to 12 inch lbs. All the panels failed theflexibility test using a inch mandrel. All the panels failed the marresistance test. All the panels passed the iodine resistance test. Allthe panels passed the 2 percent NaOH (16 hours) test. With the exceptionof the 30:70 enamel, the panels passed the acetone resistance test. Thepoor performance of these compositions, compared to the Nos. 17-22compositions, was surprising.

Thus having described the invention, what is claimed 1. An aqueouscoating composition suitable for forming a baked finish surface coating,which composition consists essentially of (A) the polyester product of(a) an acidic member selected from the class consisting of trimelliticacid, trimellitic anhydride, hemimellitic acid, hemimellitic anhydrideand trimesic acid, (b) an alkylene glycol having 2-10 carbon atoms, and(c) an alkanedioic acid having 4-10 carbon atoms, the reaction systemcontaining said acidic member/ said glycol/said alkanedioic acid inmolar ratio in the range 2.3/ 7/ 3 to 3.2/7/ 0.5, the carboxyl groupaffording reactants and hydroxyl group affording reactants beingcontrolled to provide a molar ratio hydnoxyl groups/carboxyl groupscharged to the reaction in the range of 1.05 to 1.40, and said polyesterbeing characterized by an acid number of about 25-80; (B)tetr-akis(alkoxymethyl)benzoguanamine wherein each alkoxy group has l-3carbon atoms and at least one alkoxy group is of different carbon numberthan the others, said polyester :and said benzoguanamine beingphysically blended, by weight, to make 100 parts ofpolyester:benzoguanamine blend in a proportion ranging from 95:5 toabout 30:70; and (C) aqueous alkaline medium capable of dissolving saidpolyester and said benzoguanamine in an amount sufficient to form afluid aqueous solution of said polyester and said benzoguanamine.

2. The composition of claim 1 wherein said polyester includes a modifierselected from the class consisting of alkane monocarboxylic acids having6-13 carbon atoms and alkane monohydric alcohols having 4-13 carbonatoms.

3. The composition of claim 1 wherein the acid number of said polyesteris about 30-50.

4. The composition of claim 1 wherein said proportion of saidpolyester:benzogu'anamine is about 85:15 to 40:60.

5. The composition of claim 1 wherein said acidic member is trimelliticanhydride.

6. The composition of claim 1 wherein said acidic member is tn'mesicacid.

7. The composition of claim 1 wherein said alkanedioic acid is adipicacid.

8. The composition of claim 1 wherein said alkanedioic acid is pimelicacid.

9. The composition of claim 1 wherein said benzoguanamine isdi(ethoxyrnethyl)di(methoxymethyl)benzoguanamine.

10. The composition of claim 1 wherein said benzoguanamine ismono(ethoxymethyl)tri(methoxymethyl) benzoguanamine.

11. The composition of claim 1 wherein said glycol has 4-10 carbonatoms.

12. The composition of claim 11 wherein said glycol is neopentyl glycol.

13. The composition of claim 11 wherein said glycol is 1,4-butanediol.

14. The composition of claim 1 wherein said benzoguanamine is anequilibrated mixture having at least two different alkoxy groups presentand one of these is present in an amount of at least about percent.

15. The composition of claim 14 wherein said alkoxy groups are methoxyand ethoxy in about equimolar amounts.

16. The composition of claim 14 wherein said alkoxy groups are methoxyand ethoxy in a molar ratio of about 3.

17. A fluid coating composition consisting essentially of (A) thepolyester product of (a) an acidic member selected from the classconsisting of trirnellitic acid, trimellitic anhydride, hemimelliticacid, hemimellitic anhydride and trimesic acid, (b) an alkylene glycolhaving 2-10 carbon atoms, and (c) an alkanedioic acid having 4-10 carbonatoms, the reaction system containing said acidic member/saidglycol/said alkanedi-oic acid in a molar ratio in the range of 2.3/7/3to 32/7/05, the carboxyl group affording reactants and hydroxyl groupatfording reactants being controlled to provide a molar ratio ofhydroxyl groups/carboxyl groups charged tothe reaction in the range of1.05-1.40 and said polyester being characterized by an acid number ofabout 25-80; (B) tetrakis(alkoxymethyl)benzoguanamine wherein eachalkoxy group has 1-3 carbon atoms, said polyester and saidbenzoguanamine being physically blended, by weight, to make 100 parts ofpolyester:benzoguanamine blend in a proportion ranging from :5 to 30:70;and (C) a member of the group consisting of organic solvent and aqueousalkaline medium, said member capable of dissolving said polyester andsaid benzoguanamine, in an amotmt suflicient to form a fluid compositionof said polyester and said benzoguanarnine.

18. A fluid composition suitable for use in the forming of a bakedfinish surface coating, which composition consists essentially of (A)the polyester product of (a) an acidic member selected from the classconsisting of trimellitic acid, trimellitic anhydride, hemimelliticacid, hemimellitic anhydride and trimesic acid, (b) an a lkylene glycolhaving 2-10 carbon atoms, and (c) an alkanedioic acid having 4-10 carbonatoms, the reaction system containing said acidic member/saidglycol/said alkanedioic acid in a molar ratio in the range of 2.3/7/3 to32/7/05, the carboxyl group affording reactants and hydroxyl groupaffording reactants being controlled to provide a molar ratio ofhydroxyl groups/carboxyl groups charged to the reaction in the range of1.05-1.40 and said polyester being characterized by an acid number ofabout 25-80; (B) tetrakis (:allcoxymethyl)benzoguanamine wherein eachalkoxy group has 1-3 carbon atoms, said polyester and saidbenzoguanamine being physically blended, by weight, to make parts ofpolyester:benzoguanamine blend in a proportion ranging from 95 :5 to30:70; and (C) organic solvent, capable of dissolving said polyester andsaid benzoguanamine, in an amount sufiicient to form a fluidcomposition.

19. The composition of claim 18 wherein said polyester includes amodifier selected from the class consisting of alkane monocarboxylicacids having 6-13 carbon atoms and alkane monohydric alcohols having4-13 carbon atoms.

20. The composition of claim 18 wherein the acid number of saidpolyester is about 30-50.

21. The composition of claim 18 wherein said proportion of saidpolyester:benzoguanamine blend is about 80:20 to 70:30.

22. The composition of claim 18 wherein said acidic member istrimellitic anhydride.

23. The composition of claim 18 wherein said acidic member is trimesicacid.

24. The composition of claim 18 wherein said alkanedioic acid is adipicacid.

25. The composition of claim 18 wherein said alkanedioic acid is imelicacid.

26. The composition of claim 18 wherein said benzoguanamine isN,N,N',N'-tetrakis(methoxymethyl)-2,6-di amino-4-phenyl-s-triazine.

27. The composition of claim 18 wherein said benzoguanamine isN,N,N,N-tetrakis(ethoXymethyl-2,6-diarnino-4-phenyl-s-triazine.

28. The composition of claim 18 wherein said benzoguanamine at least onealkoXy has a different number of carbon atoms than the others.

29. The composition of claim 18 wherein said solvent is a Xylene-butanolsolution.

30. The composition of claim 18 wherein said glycol has 4-10 carbonatoms.

31. The composition of claim 30 wherein said glycol is neopentyl glycol.

32. The composition of claim 30 wherein said glycol is 1,4-butaned'iol.

(References on following page) 15 16 References Cited by the Examiner3,053,783 9/62 Br-oadhead et :al. 26075 UNITED STATES PATENTS 3,102,8689/63 BOltOIl (it 8.1 260-75 1,998,744 4/35 Ubben 26075 2,448,338 8/48Widmer et a1 260 21 5 LEON I. BERCOVITZ, Przmary Examzner. 2,709,6935/55 Widmer 260 67 6 MI ON TERMAN, JAMES A. SEIDLECK, DON- 129,545 8/61Stephens 260-2499 ALD E. CZAJA, Examiners.

17. A FLUID COATING COMPOSITION CONSISTING ESSENTIALLY OF (A) THEPOLYESTER PRODUCT OF (A) AN ACIDIC MEMBER SELECTED FROM THE CLASSCONSISTING OF TRIMELLITIC ACID, TRIMELLITIC ANHYDRIDE, HEMMIMELLITICACID, HEMIMELLITIC ANHYDRIDE AND TRIMESIC ACID, (B) AN ALKYLENE GLYCOLHAVING 2-10 CARBON ATOMS, AND (C) AN ALKANEDIOIC ACID HAVING 4-10 CARBONATOMS, THE REACTION SYSTEM CONTAINING "SAID ACIDIC MEMBER/SAIDGLYCOL/SAID ALKANEDIOIC ACID" IN A MOLAR RATIO IN THE RANGE OF 2.3/7/3TO 3.2/7/0.5, THE CARBOXYL GROUP AFFORDING REACTANTS AND HYDROXYL GROUPAFFORDING REACTANTS BEING CONTROLLED TO PROVIDE A MOLAR RATIO OF"HYDROXYL GROUPS/CARBOXYL GROUPS" CHARGED TO THE REACTION IN THE RANGEOF 1.05-1.40 AND SAID POLYESTER BEING CHARACTERIZED BY AN ACID NUMBER OFABOUT 25-80; (B) TETRAKIS(ALKOXYMETHYL)BENZOGUANAMINE WHEREIN EACHALKOXY GROUP HAS 1-3 CARBON ATOMS, SAID POLYESTER AND SAIDBENZOGUANAMINE BEING PHYSICALLY BLENDED, BY WEIGHT, TO MAKE 100 PARTS OF"POLYESTER:BENZOGUANAMINE" BLEND IN A PROPORTION RANGING FROM 95:5 TO30:70; AND (C) A MEMBER OF THE ROUP CONSISTING OF ORGANIC SOLVENT ANDAQUEOUS ALKALINE MEDIUM, SAID MEMBER CAPABLE OF DISSOLVING SAIDPOLYESTER AND SAID BENZOGUANAMINE, IN AN AMOUNT SUFFICIENT TO FORM AFLUID COMPOSITION OF SAID POLYESTER AND SAID BENZOGUANAMINE.